Electrochemical cells are commonly used electrical power sources. A cell contains a negative electrode and a positive electrode. The negative electrode contains an active material that can be oxidized; the positive electrode contains or consumes an active material that can be reduced. The negative electrode active material is capable of reducing the positive electrode active material. In some embodiments, to prevent direct reaction of the positive electrode material and the negative electrode material, the negative electrode and the positive electrode are electrically isolated from each other by a separator.
When a cell is used as an electrical energy source in a device, electrical contact is made to the electrodes, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power. An electrolyte, for example, potassium hydroxide, in contact with the electrodes contains ions that flow through the separator between the electrodes to maintain charge balance throughout the cell during discharge.
In a metal-air electrochemical cell, oxygen is reduced at the positive electrode (the cathode), and a metal is oxidized at the negative electrode (the anode). Oxygen can be supplied to the cathode from the atmospheric air external to the cell through one or more air hole(s) in the cell can.
To prolong cell life, it is desirable that the cathode be isolated from air flow when not in use (e.g., to reduce carbonation), but exposed to air flow when in use. During use, it is desirable to provide uniform and sufficient air access to the cathode to provide, for example, uniform discharge of the active materials and/or a relatively high discharge voltage profile.